Electrical energy storage and flashing apparatus

ABSTRACT

This disclosure relates to electrical energy storage apparatus in which a novel clamp supply voltage and feedback control is provided in a series resonant charging energy storage system to prevent the storage elements from developing voltages that exceed a predetermined voltage and that would normally be produced by the action of the series resonant charging.

United States Patent Jacob Goldberg [56] References Cited UNITED STATES PATENTS 3,229,158 1/1966 Jensen 320/1 X 3,286,128 11/1966 Ward 315/241 3,526,821 9/1970 Thomas 315/241 X Primary Examiner-Roy Lake Assistant Examiner- Lawrence .1. Dahl Attorney-Rines and Rines ABSTRACT: This disclosure relates to electrical energy storage apparatus in which a novel clamp supply voltage and feedback control is provided in a series resonant charging energy storage system to prevent the storage elements from developing voltages that exceed a predetermined voltage and that would normally be produced by the action of the series resonant charging.

CLAMP SUPPLY 2 l 7 REFERENCE SIGNAL N R LLER MAIN FROM VOLTAGE (WITH Z E S STANDARD COMPARATOR) u I MAL PAIENTEDuuv 30 Ian INVENTOR JACOB GOLDBERG WK o Hwy] A).

ATTORNEYS E g/@200 1E5 mw ogzou ELECTRICAL ENERGY STORAGE AND FLASHING APPARATUS The present invention relates to electrical energy storage apparatus, being more particularly directed to those storage systems involving series resonant charging and the like that are particularly adapted for multiple discharges, as in the case of periodically operated multiple or flash stroboscopic and similar applications.

The art is replete with numerous types of energy storage systems adapted for storing energy in capacitor banks and other types of electrical storage elements for such purposes as delivering the stored energy at preselected instants'of time, as in stroboscopic, radar and other electrical flashing circuit applications. Among such, for example, are the flash-producing circuits disclosed in prior U.S. Pats. of the assignee of the present applications Nos. 3,354,351 issued Nov. 2 l 1967 and 3,355,625 issued Nov. 28, l967.

Particularly in such stroboscopic and related electrical flashing systems that involve series resonant charging and in which approximate voltage-doubling occurs as a result of the series resonance phenomena, voltages exceeding a desired predetermined voltage may be produced for different repetitive rates of flashing and for other varying input voltage conditions. Various expedients have been resorted to in an attempt to cause the energy storage bank to be recharged to the same predetermined value even under conditions of short and varying recharged times, varying input voltages, severe short term overload and other adverse'conditions. Included in such expedients are circuits providing zener diode sinks and the like in which excess voltage not desired in the charging process may be wasted. Such techniques, however, only approximately and roughly keep the charged voltage within the desired limit and are subject to burnout, failure of operation and other disadvantageous efiects.

An object of the present invention, accordingly, is to provide a new and improved electrical energy storage apparatus that shall not be subject to the above described disadvantages but that, to the contrary, provides for the continual and automatic insuring that the energy storage elements always recharge to the same predetermined value irrespective of varying flashing or charging times, varying the input voltages, severe overloads or other adverse conditions.

A further object is to provide such novel apparatus particularly adapted for repetitive stroboscopic and similar flashing discharges or bursts of periodic discharges.

Other and further objects will be explained hereinafter and are more particularly delineated in the appended claims. In summary, however, the invention in its preferred form, contemplates electrical energy storage apparatus having a source of direct current voltage provided with means for varying the magnitude of the voltage. Energy storage means is provided connected through a charging means to said source to store energy therein that, by the action of series resonant charging, may develop a voltage that exceeds the predetermined voltage to which it is desired to charge the energy storage means. There is further provided, in the form of a feedback path, responses to the voltage to which the energy storage means is being charged that control the voltage varying means of the source to limit the voltage developed by the series resonant charging, as stored in the energy storage means, to the said predetermined voltage. Preferred constructional details are hereinafter set forth.

The invention will now be described with reference to the accompanying drawing, the single FIGURE of which is a combined block and schematic circuit diagram illustrating the invention in preferred form.

Referring to the drawing, a conventional direct current main power supply is shown at l with its upper and lower terminals l and 1 respectively connected to a filter network comprising parallel resistor R, and capacitor C,. The upper terminal I is connected to a choke or coil L and a polarity insuring check diode CR to store energy in an energy storage bank, schematically illustrated by the capacitor C, the charging circuit being series resonant. The energy stored in the capacitance or other energy storage element or elements C may then be delivered to a load, so labeled, such as, for example, the flash tubes and other electrical discharge devices discussed in said patents, upon the closing of a normally open or nonconductive switching means, schematically illustrated at Sw, such as a silicon controlled rectifier, thyratron or other similar trigger device, as described, for example, in said patents. In operation, the energy developed in the energy storage 'means C is delivered to the load, such as the flash tube, in order to render the same conductive and to develop the flash of light or other discharge therethrough, upon the triggering or closing or rendering conductive of the switching element Sw. Following discharge of the energy stored at C, the switching device Sw again opens, and the energy storage elements C are again recharged from the main power supply I through the series resonant'circuit including the coil L and capacitance C. If the voltage of the source 1 is represented as V this recharging through L will approach a voltage 2V, which, in accordance with the invention, is controlled by a further clamp supply voltage source 2, the lower terminal of which'is shown connected to the main' power source terminal 1 and the upper terminal of which is shown connected to the upper terminal or side 3 of a potential divider or similar network 3, illustrated for purposes of explanation as a potentiometer. The divider 3 is provided with a variable sampling tap or slider S, and the lower terminal or side 3" of the same is shown returned to the lower terminal 1" of the main power source 1. The clamp supply 2 is provided with a filter R -C, such that, if the voltage developed thereacross is represented by V there will appear across the potential divider 3, a voltage V which represents the sum of V and V As before stated,it is an objective of the invention to cause the voltage energy stored in C during charging, to return to a predetermined voltage irrespective of the ringing or oscillating performance of the series resonant charging, and despite different charging rates, overloads and other varying conditions. The capacitor(s) in the energy storage bank C' will tend to charge toward voltage 2V,, as before explained. But the excess charging above the voltage (V +V will be delivered to capacitor C through diode CR which is bridged by resistor R thus commencing to raise the voltage V This rise or increase in V reflects a corresponding increase in the voltage V a sample of which is present at the tap or slider S. In accordance with the invention, that sample is fed back by the feedback path 5 to adjust or control the voltage of the main source 1 in accordance with variations in V and continually to adjust the source 1, accordingly; in this instance, to assume a lower voltage such that (V,+V,) continues to remain at the predetermined value V This process will continue for each pulse, such that ultimately the main source 1 will deliver precisely that voltage which will cause the energy storage C to become resonantly charged to the value measured at V with no excess beyond that necessary to sustain the small stray loss incurred in the sampling potentiometer 3 and the small residual error necessary to actuate the control or adjusting system at the source I. That control is shown in the form of a conventional comparator circuit illustrated at 7 which compares sample voltage fed back along 5 with a standard or reference signal, so labeled, in order to produce the error signal for adjusting the source 1. This comparison and control may be effected with many types of well-known circuits of this character including, for example, that described in an article entitled Pulse Width Modulated Voltage Regulator" appearing in Delco Radio Application Note 98, published May, 1965; or any other well-known system of this nature.

The time necessary for the system to achieve this equilibrium will, of course, vary with repetitive rate and details of the design, and a few cycles will be necessary to shift the system to the operating equilibrium. Should a relatively long interval exist between two successive cycles, the system will tend to revert to the initial condition existent before repetitive operation began. In general, however, for the applications abovedescribed, the interval between cycles will be very short compared to the time required to return to the initial condition such that the operation will proceed under the equilibrium conditions. Thus, the value of C is selected such that the excessenergy associated with the early cycles will be sufficient to increase its voltage by an amount that is greater than the loss or drop in voltage of C due to providing the recharged energy.

As an illustration, the circuit shown in the drawing has been successfully operated for one second repetitive bursts of 256 flashes (occurring in about one-tenth of a second), with twoelectrode zenon flash tubes such as those described in said patents, with the voltage level maintained substantially constant on the recharge of capacitor C throughout the burst of flashes. In this instance, the voltage V had a value of about 350 volts, and the voltage V about 250 volts.

Further modifications will occur to those skilled in the art and all such are considered to fall within the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. Electrical energy storage apparatus having, in combination, a source of direct-current voltage provided with means for varying the magnitude of its voltage, energy-storage means connected in a series resonant charging circuit to said source to store energy in the energy storage means that, by the action of the series resonant charging, may develop a voltage that exceeds a predetermined voltage to which it is desired to charge the energy-storage means, and means responsive to the voltage to which the energy-storage means is being charged and connected with the said voltage-magnitude varying means of the source to limit the voltage developed by the series resonant charging to the said predetermined voltage.

2. Apparatus as claimed in claim 1 and in which load means is connected in series with normally open switch means'in parallel with the said energy storage means for delivering the said predetermined voltage developed in the energy storage means to the load means when the switch means is closed.

3. Apparatus as claimed in claim 2 and in which the said responsive means comprises potential divider means connected to provide a sample voltage indicative of the said voltage developed in the energy storage means, and feedback means is connected between said potential divider and said source varying means.

4. Apparatus as claimed in claim 3 and in which there is provided a further voltage supply, one terminal of which is connected to one terminal of the said source and the other terminal of which is connected to one side of the said potential divider means, the other side of the potential divider means being connected with the other terminal of the said source to develop across the potential divider means the sum of the voltage of the said source and that of the further voltage supply.

5. Apparatus as claimed in claim 4 and in which the said feedback means includes a voltage controller provided with comparator means for comparing the voltage fed back from said potential divider means with a reference voltage in order to vary the source in accordance with variations in the voltage developed in the energy storage means.

6. Apparatus as claimed in claim 3 and in which said load comprises a normally nonconductive flash device that is rendered conductive upon application of a threshold voltage from the energy storage means upon closing of the said switch means.

7. Apparatus as claimed in claim 4 and in which said further voltage supply comprises further energy-storage means connected to the first-recited energy-storage means for the transfer of energy therebetween.

8. Apparatus as claimed in claim 7 and in which said further and said first-recited energy-storage means are connected by rectifier means bridged by resistance means.

9. Apparatus as claimed in claim 7 and in which said further energy-storage means is shunted by resistance means.

10. Apparatus as claimed in claim 9 and in which a filter including parallel resistance and capacitance is connected across said source.

11. Electrical energy storage apparatus having, in combination, first energy-storage means, direct-current voltage source means coupled to said energy-storage means and capable of developing a voltage that exceeds a predetermined voltage to which it is desired to charge the energy-storage means, and means for regulating the voltage to which said energy-storage means is charged, said regulating means comprising further energy-storage means coupled to the first-recited energystorage means for the transfer of energy therebetween, and a voltage supply coupled to said further energy-storage means and in series with said source.

12. Apparatus as claimed in claim 11 and in which said further energy-storage means is connected to the first-recited energy-storage means by rectifier means bridged by resistance means.

13. Apparatus as claimed in claim 12 and in which load means is connected in series with normally open switch means in parallel with the first-recited energy-storage means for delivering the said predetermined voltage developed in the first-recited energy-storage means to the load means when the switch means is closed.

14. Apparatus as claimed in claim 11 and in which said source is provided with means for varying the voltage thereof in accordance with the voltage developed across the firstrecited energy-storage means.

II! I! i 

1. Electrical energy storage apparatus having, in combination, a source of direct-current voltage provided with means for varying the magnitude of its voltage, energy-storage means connected in a series resonant charging circuit to said source to store energy in the energy storage means that, by the action of the series resonant charging, may develop a voltage that exceeds a predetermined voltage to which it is desired to charge the energy-storage means, and means responsive to the voltage to which the energy-storage means is being charged and connected with the said voltage-magnitude varying means of the source to limit the voltage developed by the series resonant charging to the said predetermined voltage.
 2. Apparatus as claimed in claim 1 and in which load means is connected in series with normally open switch means in parallel with the said energy storage means for delivering the said predetermined voltage developed in the energy storage means to the loAd means when the switch means is closed.
 3. Apparatus as claimed in claim 2 and in which the said responsive means comprises potential divider means connected to provide a sample voltage indicative of the said voltage developed in the energy storage means, and feedback means is connected between said potential divider and said source varying means.
 4. Apparatus as claimed in claim 3 and in which there is provided a further voltage supply, one terminal of which is connected to one terminal of the said source and the other terminal of which is connected to one side of the said potential divider means, the other side of the potential divider means being connected with the other terminal of the said source to develop across the potential divider means the sum of the voltage of the said source and that of the further voltage supply.
 5. Apparatus as claimed in claim 4 and in which the said feedback means includes a voltage controller provided with comparator means for comparing the voltage fed back from said potential divider means with a reference voltage in order to vary the source in accordance with variations in the voltage developed in the energy storage means.
 6. Apparatus as claimed in claim 3 and in which said load comprises a normally nonconductive flash device that is rendered conductive upon application of a threshold voltage from the energy storage means upon closing of the said switch means.
 7. Apparatus as claimed in claim 4 and in which said further voltage supply comprises further energy-storage means connected to the first-recited energy-storage means for the transfer of energy therebetween.
 8. Apparatus as claimed in claim 7 and in which said further and said first-recited energy-storage means are connected by rectifier means bridged by resistance means.
 9. Apparatus as claimed in claim 7 and in which said further energy-storage means is shunted by resistance means.
 10. Apparatus as claimed in claim 9 and in which a filter including parallel resistance and capacitance is connected across said source.
 11. Electrical energy storage apparatus having, in combination, first energy-storage means, direct-current voltage source means coupled to said energy-storage means and capable of developing a voltage that exceeds a predetermined voltage to which it is desired to charge the energy-storage means, and means for regulating the voltage to which said energy-storage means is charged, said regulating means comprising further energy-storage means coupled to the first-recited energy-storage means for the transfer of energy therebetween, and a voltage supply coupled to said further energy-storage means and in series with said source.
 12. Apparatus as claimed in claim 11 and in which said further energy-storage means is connected to the first-recited energy-storage means by rectifier means bridged by resistance means.
 13. Apparatus as claimed in claim 12 and in which load means is connected in series with normally open switch means in parallel with the first-recited energy-storage means for delivering the said predetermined voltage developed in the first-recited energy-storage means to the load means when the switch means is closed.
 14. Apparatus as claimed in claim 11 and in which said source is provided with means for varying the voltage thereof in accordance with the voltage developed across the first-recited energy-storage means. 